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<p>Comparison operators are binary operators that test a condition and return <b>1</b> if that condition is logically <b>true</b> and <b>0</b> if that condition is <b>false</b>.
</p>
<table class="wikitable" style="font-size:85%;">

<tr style="text-align:center">
<th> Operator
</th>
<th> Operator name
</th>
<th> Example
</th>
<th> Description
</th></tr>
<tr style="text-align:center">
<td> <span class="t-c"><span class="mw-geshi c source-c"><span class="sy1">==</span></span></span>
</td>
<td> equal to
</td>
<td> <span class="t-c"><span class="mw-geshi c source-c">a <span class="sy1">==</span> b</span></span>
</td>
<td> <b>a</b> is equal to <b>b</b>
</td></tr>
<tr style="text-align:center">
<td> <span class="t-c"><span class="mw-geshi c source-c"><span class="sy3">!</span><span class="sy1">=</span></span></span>
</td>
<td> not equal to
</td>
<td> <span class="t-c"><span class="mw-geshi c source-c">a <span class="sy3">!</span><span class="sy1">=</span> b</span></span>
</td>
<td> <b>a</b> is not equal to <b>b</b>
</td></tr>
<tr style="text-align:center">
<td> <span class="t-c"><span class="mw-geshi c source-c"><span class="sy1">&lt;</span></span></span>
</td>
<td> less than
</td>
<td> <span class="t-c"><span class="mw-geshi c source-c">a <span class="sy1">&lt;</span> b</span></span>
</td>
<td> <b>a</b> is less than <b>b</b>
</td></tr>
<tr style="text-align:center">
<td> <span class="t-c"><span class="mw-geshi c source-c"><span class="sy1">&gt;</span></span></span>
</td>
<td> greater than
</td>
<td> <span class="t-c"><span class="mw-geshi c source-c">a <span class="sy1">&gt;</span> b</span></span>
</td>
<td> <b>a</b> is greater than <b>b</b>
</td></tr>
<tr style="text-align:center">
<td> <span class="t-c"><span class="mw-geshi c source-c"><span class="sy1">&lt;=</span></span></span>
</td>
<td> less than or equal to
</td>
<td> <span class="t-c"><span class="mw-geshi c source-c">a <span class="sy1">&lt;=</span> b</span></span>
</td>
<td> <b>a</b> is less than or equal to <b>b</b>
</td></tr>
<tr style="text-align:center">
<td> <span class="t-c"><span class="mw-geshi c source-c"><span class="sy1">&gt;=</span></span></span>
</td>
<td> greater than or equal to
</td>
<td> <span class="t-c"><span class="mw-geshi c source-c">a <span class="sy1">&gt;=</span> b</span></span>
</td>
<td> <b>a</b> is greater than or equal to <b>b</b>
</td></tr></table>
<h3><span class="mw-headline" id="Relational_operators">Relational operators</span></h3>
<p>The relational operator expressions have the form 
</p>
<table class="t-sdsc-begin">

<tr>
<td colspan="10" class="t-sdsc-sep">
</td></tr>
<tr class="t-sdsc">
<td> <span class="t-spar">lhs</span> <code><b>&lt;</b></code> <span class="t-spar">rhs</span>
</td>
<td> (1)
</td>
<td class="t-sdsc-nopad">
</td></tr>



<tr>
<td colspan="10" class="t-sdsc-sep">
</td></tr>
<tr class="t-sdsc">
<td> <span class="t-spar">lhs</span> <code><b>&gt;</b></code> <span class="t-spar">rhs</span>
</td>
<td> (2)
</td>
<td class="t-sdsc-nopad">
</td></tr>



<tr>
<td colspan="10" class="t-sdsc-sep">
</td></tr>
<tr class="t-sdsc">
<td> <span class="t-spar">lhs</span> <code><b>&lt;=</b></code> <span class="t-spar">rhs</span>
</td>
<td> (3)
</td>
<td class="t-sdsc-nopad">
</td></tr>



<tr>
<td colspan="10" class="t-sdsc-sep">
</td></tr>
<tr class="t-sdsc">
<td> <span class="t-spar">lhs</span> <code><b>&gt;=</b></code> <span class="t-spar">rhs</span>
</td>
<td> (4)
</td>
<td class="t-sdsc-nopad">
</td></tr>



<tr>
<td colspan="10" class="t-sdsc-sep">
</td></tr></table>
<div class="t-li1"><span class="t-li">1)</span> less-than expression</div>
<div class="t-li1"><span class="t-li">2)</span> greater-than expression</div>
<div class="t-li1"><span class="t-li">3)</span> less or equal expression</div>
<div class="t-li1"><span class="t-li">4)</span> greater or equal expression
<p>where 
</p>
<table class="t-par-begin">


<tr class="t-par">
<td> <span class="t-spar">lhs</span>, <span class="t-spar">rhs</span>
</td>
<td> -
</td>
<td>  expressions that both have real type or both have pointer to object type
</td></tr></table></div>
<p>The type of any relational operator expression is <span class="t-c"><span class="mw-geshi c source-c"><span class="kw4">int</span></span></span>, and its value (which is not an lvalue) is <span class="t-c"><span class="mw-geshi c source-c"><span class="nu0">1</span></span></span> when the specified relationship holds true and <span class="t-c"><span class="mw-geshi c source-c">​<span class="nu0">0</span>​</span></span> when the specified relationship does not hold.
</p><p>If <span class="t-spar">lhs</span> and <span class="t-spar">rhs</span> are expressions of any <a href="types.html" title="c/language/types" class="mw-redirect">real type</a>, then
</p>
<ul><li> <a href="conversion.html#Usual_arithmetic_conversions" title="c/language/conversion">usual arithmetic conversions</a> are performed
</li><li> the values of the operands after conversion are compared in the usual mathematical sense (except that positive and negative zeroes compare equal and any comparison involving a NaN value returns zero)
</li></ul>
<p>Note that complex and imaginary numbers cannot be compared with these operators.
</p><p>If <span class="t-spar">lhs</span> and <span class="t-spar">rhs</span> are expressions of pointer type, they must be both pointers to objects of <a href="types.html#Compatible_types" title="c/language/types" class="mw-redirect">compatible types</a>, except that qualifications of the pointed-to objects are ignored.
</p>
<ul><li> a pointer to an object that is not an element of an array is treated as if it were pointing to an element of an array with one element
</li><li> if two pointers point to the same object, or both point one past the end of the same array, they compare equal
</li><li> if two pointers point to different elements of the same array, the one pointing at the element with the larger index compares greater.
</li><li> if one pointer points to the element of an array and the other pointer points one past the end of the same array, the one-past-the-end pointer compares greater
</li><li> if the two pointers point to members of the same <a href="struct.html" title="c/language/struct">struct</a>, the pointer to the member declared later in the struct definition compares greater than then pointer to the member declared earlier.
</li><li> pointers to members of the same union compare equal
</li><li> all other pointer comparisons invoke undefined behavior
</li></ul>
<div class="t-example"><div class="t-example-live-link"><div class="coliru-btn coliru-btn-run-init">Run this code</div></div>
<div dir="ltr" class="mw-geshi" style="text-align: left;"><div class="c source-c"><pre class="de1"><span class="co2">#include &lt;assert.h&gt;</span>
<span class="kw4">int</span> main<span class="br0">(</span><span class="kw4">void</span><span class="br0">)</span>
<span class="br0">{</span>
    <a href="../error/assert.html"><span class="kw407">assert</span></a><span class="br0">(</span><span class="nu0">1</span> <span class="sy1">&lt;</span> <span class="nu0">2</span><span class="br0">)</span><span class="sy4">;</span>
    <a href="../error/assert.html"><span class="kw407">assert</span></a><span class="br0">(</span><span class="nu0">2</span><span class="sy2">+</span><span class="nu0">2</span> <span class="sy1">&lt;=</span> <span class="nu16">4.0</span><span class="br0">)</span><span class="sy4">;</span> <span class="co1">// int converts to double, two 4.0's compare equal</span>
 
    <span class="kw1">struct</span> <span class="br0">{</span> <span class="kw4">int</span> x,y<span class="sy4">;</span> <span class="br0">}</span> s<span class="sy4">;</span>
    <a href="../error/assert.html"><span class="kw407">assert</span></a><span class="br0">(</span><span class="sy3">&amp;</span>s.<span class="me1">x</span> <span class="sy1">&lt;</span> <span class="sy3">&amp;</span>s.<span class="me1">y</span><span class="br0">)</span><span class="sy4">;</span> <span class="co1">// struct members compare in order of declaration</span>
 
    <span class="kw4">double</span> d <span class="sy1">=</span> <span class="nu16">0.0</span><span class="sy2">/</span><span class="nu16">0.0</span><span class="sy4">;</span> <span class="co1">// NaN</span>
    <a href="../error/assert.html"><span class="kw407">assert</span></a><span class="br0">(</span> <span class="sy3">!</span><span class="br0">(</span>d <span class="sy1">&lt;</span> d<span class="br0">)</span> <span class="br0">)</span><span class="sy4">;</span>
    <a href="../error/assert.html"><span class="kw407">assert</span></a><span class="br0">(</span> <span class="sy3">!</span><span class="br0">(</span>d <span class="sy1">&gt;</span> d<span class="br0">)</span> <span class="br0">)</span><span class="sy4">;</span>
    <a href="../error/assert.html"><span class="kw407">assert</span></a><span class="br0">(</span> <span class="sy3">!</span><span class="br0">(</span>d <span class="sy1">&gt;=</span> d<span class="br0">)</span> <span class="br0">)</span><span class="sy4">;</span>
    <a href="../error/assert.html"><span class="kw407">assert</span></a><span class="br0">(</span> <span class="sy3">!</span><span class="br0">(</span>d <span class="sy1">&gt;=</span> d<span class="br0">)</span> <span class="br0">)</span><span class="sy4">;</span>
 
    <span class="kw4">float</span> f <span class="sy1">=</span> <span class="nu16">0.1</span><span class="sy4">;</span> <span class="co1">// f = 0.100000001490116119384765625</span>
    <span class="kw4">double</span> g <span class="sy1">=</span> <span class="nu16">0.1</span><span class="sy4">;</span> <span class="co1">// g = 0.1000000000000000055511151231257827021181583404541015625</span>
    <a href="../error/assert.html"><span class="kw407">assert</span></a><span class="br0">(</span>f <span class="sy1">&gt;</span> g<span class="br0">)</span><span class="sy4">;</span> <span class="co1">// different values</span>
<span class="br0">}</span></pre></div></div>
</div>
<h3><span class="mw-headline" id="Equality_operators">Equality operators</span></h3>
<p>The equality operator expressions have the form 
</p>
<table class="t-sdsc-begin">

<tr>
<td colspan="10" class="t-sdsc-sep">
</td></tr>
<tr class="t-sdsc">
<td> <span class="t-spar">lhs</span> <code><b>==</b></code> <span class="t-spar">rhs</span>
</td>
<td> (1)
</td>
<td class="t-sdsc-nopad">
</td></tr>



<tr>
<td colspan="10" class="t-sdsc-sep">
</td></tr>
<tr class="t-sdsc">
<td> <span class="t-spar">lhs</span> <code><b>!=</b></code> <span class="t-spar">rhs</span>
</td>
<td> (2)
</td>
<td class="t-sdsc-nopad">
</td></tr>



<tr>
<td colspan="10" class="t-sdsc-sep">
</td></tr></table>
<div class="t-li1"><span class="t-li">1)</span> equal-to expression</div>
<div class="t-li1"><span class="t-li">2)</span> not equal to expression
<p>where 
</p>
<table class="t-par-begin">


<tr class="t-par">
<td> <span class="t-spar">lhs</span>, <span class="t-spar">rhs</span>
</td>
<td> -
</td>
<td>  expressions that
<ul><li> both have any <a href="arithmetic_types.html" title="c/language/arithmetic types">arithmetic types</a> (including complex and imaginary)
</li><li> both are pointers to objects or functions of <a href="types.html#Compatible_types" title="c/language/types" class="mw-redirect">compatible</a> types, ignoring qualifiers of the pointed-to types
</li><li> one is a pointer to object and the other is a pointer to (possibly qualified) <span class="t-c"><span class="mw-geshi c source-c"><span class="kw4">void</span></span></span>
</li><li> one is a pointer to object or function and the other is a null pointer constant such as <span class="t-lc"><a href="../types/NULL.html" title="c/types/NULL">NULL</a></span>
</li></ul>
<p><br>
</p>
</td></tr></table></div>
<p>The type of any equality operator expression is <span class="t-c"><span class="mw-geshi c source-c"><span class="kw4">int</span></span></span>, and its value (which is not an lvalue) is <span class="t-c"><span class="mw-geshi c source-c"><span class="nu0">1</span></span></span> when the specified relationship holds true and <span class="t-c"><span class="mw-geshi c source-c">​<span class="nu0">0</span>​</span></span> when the specified relationship does not hold.
</p>
<ul><li> if both operands have arithmetic types, <a href="conversion.html#Usual_arithmetic_conversions" title="c/language/conversion">usual arithmetic conversions</a> are performed and the resulting values are compared in the usual mathematical sense (except that positive and negative zeroes compare equal and any comparison involving a NaN value, including equality with itself, returns zero). In particular, values of complex type are equal if their real parts compare equal and their imaginary parts compare equal.
</li><li> if one operand is a pointer and the other is a null pointer constant, the null pointer constant is first <a href="conversion.html" title="c/language/conversion">converted</a> to the type of the pointer (which gives a null pointer value), and the two pointers are compared as described below
</li><li> if one operand is a pointer and the other is a pointer to void, the non-void pointer is <a href="conversion.html" title="c/language/conversion">converted</a> to the pointer to void and the two pointers are compared as described below
</li><li> two pointers compare equal if any of the following is true:
</li></ul>
<dl><dd><ul><li> they are both null pointer values of their type
</li><li> they are both pointers to the same object
</li><li> one pointer is to a struct/union/array object and the other is to its first member/any member/first element
</li><li> they are both pointing one past the last element of the same array
</li><li> one is one past the end of an array, and the other is at the start of a different array (of the same type) that follows the first in a larger array or in a struct with no padding
</li></ul>
</dd></dl>
<p>(as with relational operators, pointers to objects that aren't elements of any array behave as pointers to elements of arrays of size 1)
</p>
<h4><span class="mw-headline" id="Notes">Notes</span></h4>
<p>Objects of struct type do not compare equal automatically, and comparing them with <span class="t-lc"><a href="../string/byte/memcmp.html" title="c/string/byte/memcmp">memcmp</a></span> is not reliable because the padding bytes may have any values.
</p><p>Because pointer comparison works with pointers to void, the macro <span class="t-lc"><a href="../types/NULL.html" title="c/types/NULL">NULL</a></span> may be defined as <span class="t-c"><span class="mw-geshi c source-c"><span class="br0">(</span><span class="kw4">void</span><span class="sy2">*</span><span class="br0">)</span><span class="nu0">0</span></span></span> in C, although that would be invalid in C++ where void pointers do not implicitly convert to typed pointers
</p><p>Care must be taken when comparing floating-point values for equality, because the results of many operations cannot be represented exactly and must be rounded. In practice, floating-point numbers are usually compared allowing for the difference of one or more units of the last place.
</p>
<div class="t-example"><div class="t-example-live-link"><div class="coliru-btn coliru-btn-run-init">Run this code</div></div>
<div dir="ltr" class="mw-geshi" style="text-align: left;"><div class="c source-c"><pre class="de1"><span class="co2">#include &lt;assert.h&gt;</span>
<span class="kw4">int</span> main<span class="br0">(</span><span class="kw4">void</span><span class="br0">)</span>
<span class="br0">{</span>
    <a href="../error/assert.html"><span class="kw407">assert</span></a><span class="br0">(</span><span class="nu0">2</span><span class="sy2">+</span><span class="nu0">2</span> <span class="sy1">==</span> <span class="nu16">4.0</span><span class="br0">)</span><span class="sy4">;</span> <span class="co1">// int converts to double, two 4.0's compare equal</span>
 
    <span class="kw4">int</span> n<span class="br0">[</span><span class="nu0">2</span><span class="br0">]</span><span class="br0">[</span><span class="nu0">3</span><span class="br0">]</span> <span class="sy1">=</span> <span class="br0">{</span><span class="nu0">1</span>,<span class="nu0">2</span>,<span class="nu0">3</span>,<span class="nu0">4</span>,<span class="nu0">5</span>,<span class="nu0">6</span><span class="br0">}</span><span class="sy4">;</span>
    <span class="kw4">int</span><span class="sy2">*</span> p1 <span class="sy1">=</span> <span class="sy3">&amp;</span>n<span class="br0">[</span><span class="nu0">0</span><span class="br0">]</span><span class="br0">[</span><span class="nu0">2</span><span class="br0">]</span><span class="sy4">;</span> <span class="co1">// last element in the first row</span>
    <span class="kw4">int</span><span class="sy2">*</span> p2 <span class="sy1">=</span> <span class="sy3">&amp;</span>n<span class="br0">[</span><span class="nu0">1</span><span class="br0">]</span><span class="br0">[</span><span class="nu0">0</span><span class="br0">]</span><span class="sy4">;</span> <span class="co1">// start of second row</span>
    <a href="../error/assert.html"><span class="kw407">assert</span></a><span class="br0">(</span>p1<span class="sy2">+</span><span class="nu0">1</span> <span class="sy1">==</span> p2<span class="br0">)</span><span class="sy4">;</span> <span class="co1">// compare equal</span>
 
    <span class="kw4">double</span> d <span class="sy1">=</span> <span class="nu16">0.0</span><span class="sy2">/</span><span class="nu16">0.0</span><span class="sy4">;</span> <span class="co1">// NaN</span>
    <a href="../error/assert.html"><span class="kw407">assert</span></a><span class="br0">(</span> d <span class="sy3">!</span><span class="sy1">=</span> d <span class="br0">)</span><span class="sy4">;</span> <span class="co1">// NaN does not equal itself</span>
 
    <span class="kw4">float</span> f <span class="sy1">=</span> <span class="nu16">0.1</span><span class="sy4">;</span> <span class="co1">// f = 0.100000001490116119384765625</span>
    <span class="kw4">double</span> g <span class="sy1">=</span> <span class="nu16">0.1</span><span class="sy4">;</span> <span class="co1">// g = 0.1000000000000000055511151231257827021181583404541015625</span>
    <a href="../error/assert.html"><span class="kw407">assert</span></a><span class="br0">(</span>f <span class="sy3">!</span><span class="sy1">=</span> g<span class="br0">)</span><span class="sy4">;</span> <span class="co1">// different values</span>
<span class="br0">}</span></pre></div></div>
</div>
<h3><span class="mw-headline" id="References">References</span></h3>
<div class="t-ref-std-11">
<ul><li> C11 standard (ISO/IEC 9899:2011): 
</li></ul>
<dl><dd><ul><li> 6.5.8 Relational operators (p: 95-96)
</li></ul>
</dd></dl>
<dl><dd><ul><li> 6.5.9 Equality operators (p: 96-97)
</li></ul>
</dd></dl>
<div class="t-ref-std-c99">
<ul><li> C99 standard (ISO/IEC 9899:1999): 
</li></ul>
<dl><dd><ul><li> 6.5.8 Relational operators (p: 85-86)
</li></ul>
</dd></dl>
<dl><dd><ul><li> 6.5.9 Equality operators (p: 86-87)
</li></ul>
</dd></dl>
<div class="t-ref-std-c89">
<ul><li> C89/C90 standard (ISO/IEC 9899:1990): 
</li></ul>
<dl><dd><ul><li> 3.3.8 Relational operators 
</li></ul>
</dd></dl>
<dl><dd><ul><li> 3.3.9 Equality operators 
</li></ul>
</dd></dl>
</div>
<h3><span class="mw-headline" id="See_also">See also</span></h3>
<p><a href="operator_precedence.html" title="c/language/operator precedence"> Operator precedence</a>
</p>
<table class="wikitable">

<tr style="text-align:center">
<th colspan="7"> Common operators
</th></tr>
<tr style="text-align:center">
<td> <a href="operator_assignment.html" title="c/language/operator assignment"> assignment</a>
</td>
<td> <a href="operator_incdec.html" title="c/language/operator incdec"> increment<br>decrement</a>
</td>
<td> <a href="operator_arithmetic.html" title="c/language/operator arithmetic"> arithmetic</a>
</td>
<td> <a href="operator_logical.html" title="c/language/operator logical"> logical</a>
</td>
<td> <strong class="selflink"> comparison</strong>
</td>
<td> <a href="operator_member_access.html" title="c/language/operator member access"> member<br>access</a>
</td>
<td> <a href="operator_other.html" title="c/language/operator other"> other</a>
</td></tr>
<tr style="text-align:center">
<td>
<p><span class="t-c"><span class="mw-geshi c source-c">a <span class="sy1">=</span> b<br>
a <span class="sy2">+</span><span class="sy1">=</span> b<br>
a <span class="sy2">-</span><span class="sy1">=</span> b<br>
a <span class="sy2">*</span><span class="sy1">=</span> b<br>
a <span class="sy2">/</span><span class="sy1">=</span> b<br>
a <span class="sy2">%</span><span class="sy1">=</span> b<br>
a <span class="sy3">&amp;</span><span class="sy1">=</span> b<br>
a <span class="sy3">|</span><span class="sy1">=</span> b<br>
a <span class="sy3">^</span><span class="sy1">=</span> b<br>
a <span class="sy1">&lt;&lt;=</span> b<br>
a <span class="sy1">&gt;&gt;=</span> b</span></span>
</p>
</td>
<td>
<p><span class="t-c"><span class="mw-geshi c source-c"><span class="sy2">++</span>a<br>
<span class="sy2">--</span>a<br>
a<span class="sy2">++</span><br>
a<span class="sy2">--</span></span></span>
</p>
</td>
<td>
<p><span class="t-c"><span class="mw-geshi c source-c"><span class="sy2">+</span>a<br>
<span class="sy2">-</span>a<br>
a <span class="sy2">+</span> b<br>
a <span class="sy2">-</span> b<br>
a <span class="sy2">*</span> b<br>
a <span class="sy2">/</span> b<br>
a <span class="sy2">%</span> b<br>
~a<br>
a <span class="sy3">&amp;</span> b<br>
a <span class="sy3">|</span> b<br>
a <span class="sy3">^</span> b<br>
a <span class="sy1">&lt;&lt;</span> b<br>
a <span class="sy1">&gt;&gt;</span> b</span></span>
</p>
</td>
<td>
<p><span class="t-c"><span class="mw-geshi c source-c"><span class="sy3">!</span>a<br>
a <span class="sy3">&amp;&amp;</span> b<br>
a <span class="sy3">||</span> b</span></span>
</p>
</td>
<td>
<p><span class="t-c"><span class="mw-geshi c source-c">a <span class="sy1">==</span> b<br>
a <span class="sy3">!</span><span class="sy1">=</span> b<br>
a <span class="sy1">&lt;</span> b<br>
a <span class="sy1">&gt;</span> b<br>
a <span class="sy1">&lt;=</span> b<br>
a <span class="sy1">&gt;=</span> b</span></span>
</p>
</td>
<td>
<p><span class="t-c"><span class="mw-geshi c source-c">a<span class="br0">[</span>b<span class="br0">]</span><br>
<span class="sy2">*</span>a<br>
<span class="sy3">&amp;</span>a<br>
a<span class="sy2">-</span><span class="sy1">&gt;</span>b<br>
a.<span class="me1">b</span></span></span>
</p>
</td>
<td>
<p><span class="t-c"><span class="mw-geshi c source-c">a<span class="br0">(</span>...<span class="br0">)</span><br>
a, b<br>
<span class="br0">(</span>type<span class="br0">)</span> a<br>
<span class="sy4">?</span> <span class="sy4">:</span><br>
<span class="kw4">sizeof</span><br>
_Alignof</span></span> <span class="t-mark-rev t-since-c11">(since C11)</span>
</p>
</td></tr>
</table>
<table class="t-dsc-begin">

</table></div>
</div>

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